Conventional drum type automatic washing machines include a perforated cylindrical drum mounted for rotation about a horizontal axis within a fixed, closed water tank. Garments or other items to be washed are placed in the rotatable cylindrical drum, typically through a front opening door to the drum, or alternatively through an opening in the side wall of the drum. In either case, the opening of the drum is closed, and the water tank closed.
Water is introduced into the water tank, filling the tank to a predetermined level. The water may be heated either before filling the tank, within the tank by a heater or may be removed from the water tank and heated before being reintroduced into the tank. The water within the water tank enters the cylindrical drum through the perforations in the cylindrical drum or through the shaft. The cylindircal drum is then rotated about its axis to agitate the items to be washed and to pass these through the washing water.
After completion of the washing cycle, the washing water is removed from the water tank, and hence from the cylindrical drum via an outlet. The outlet is typically in the form of a valve which allows water to drain from the water tank by gravity, or is a pump. Clean water for rinsing is then introduced to the water tank and hence into the cylindrical drum. The drum is again rotated to agitate the items within the drum. The rinsing water is then removed from the water tank in the same way as the washing water.
It is desirable to increase the capacity of drum type washing machines to allow washing of larger loads. Washing machines, as with other household appliances, are generally manufactured to a standard size to fit into a standard size space below and between kitchen units. Accordingly, it is desirable that the overall size of the washing machine should remain the same as conventional washing machines. In a conventional washing machine, the size of the cylindrical drum which receives the items to be washed cannot be increased significantly without increasing the size of the water tank in which the drum is provided. The water tank cannot be enlarged without increasing the overall size of the machine, and it is therefore not possible to increase the capacity of a conventional washing machine whilst keeping the overall machine size unchanged.
One solution to this problem is to dispense with the separate water tank and cylindrical rotatable drum, and instead provide a single rotatable drum which both receives the items to be washed and contains all the water for washing and rinsing items. A single drum washing machine is disclosed in U.S. Pat. No. 4,941,333.
A problem with single drum washing machines is that, unlike conventional machines with a fixed water tank, it is difficult to provide heaters, water level detectors and water outlets below the water level in the rotatable water tank, firstly due to the difficulty in making a physical or electrical connection between the fixed body of the machine and the rotating drum, and secondly as a water outlet, heater or detector fixed on a rotating drum will rotate with the drum and hence move above the level of the water as the drum is rotated unless the outlet, heater or detector is provided axially. Even where the outlet is provided axially, the outlet, heater or detector will usually be above the height of the water.
In U.S. Pat. No. 4,941,333, the single drum is provided with an inclined side wall having a larger diameter at the back end than at the open front end. To remove water, the drum is rotated at a high speed forcing water within the drum, by centrifugal force, to the side walls of the drum and, due to the inclined sides, towards the rear of the drum. A fixed wiper blade is mounted on the axle of the drum, which does not rotate, the wiper abutting the rear of the side wall of the drum. As water is forced to the rear of the side wall, the water is wiped from the side wall by the wiper, and runs down the wiper blade to a centrally located outlet.
Such high speed rotation is disadvantageous as water can only be removed when the drum is rotated at high speed, it is not possible to remove water during a wash cycle, and it is therefore not possible to recirculate and reheat the water.
Washing machines are used not only for washing items of clothing, but may also be used for dying of garments. In this case, the washing water is replaced by a suitable dye, but in other respects the washing cycle is unchanged.